Develop new or improved methods for organ culture of the intestinal mucosa, especially in systems in which it will eventually be possible to study agents and mechanisms involved in carcinogenesis and anti-carcinogenesis. Although some work has been done on this topic, the problem requires even more emphasis and investigation in systematic detail. Thus, it is desired to: optimize organ culture conditions so that the duration of in vitro experiments can be extended beyond a few weeks; investigate in culture various aspects of lesion development and metabolism subsequent to treatment with known or suspected carcinogens, cocarcinogens, promotors, and other substances; perform similar studies on explants of colon transplanted to whole animals; and perform long-term experiments in an attempt to demonstrate that organ cultures of intestinal mucosa and/or immediate explants to intact animals are capable of developing frank carcinoma and/or other indications of appropriate histopathology upon transplantation to an intact animal.